Psoriasis is a common inflammatory skin disorder characterized by T lymphocyte infiltration, epidermal hyperkeratosis, and increased angiogenesis. The factors that initiate and maintain the psoriatic process are not well understood. We know that psoriasis can be exacerbated by systemic administration of Thl cytokines and lithium, and can be alleviated by glucocorticoids, methotrexate, and ultraviolet light. We have demonstrated in a transgenic mouse model that over expresses IL-7, an angiogenic phenotype closely resembling human psoriasis. In addition, IL-7 is highly expressed in human psoriasis and can be down regulated by ultraviolet light, which may account for some of the beneficial properties of this therapy in psoriasis. l) We will determine the cell lineages that synthesize IL-7 and express its cognate receptor, IL-7R, in psoriasis 2) We will determine whether factors known to aggravate psoriasis, such Thl cytokines and lithium regulate IL-7 secretion and synthesis. 3 ) We will determine whether angiogenic factors such as vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFUF) regulate IL- 7 synthesis and secretion.